Abstract
Assessment and treatment of the VLBW infant with cardiovascular impairment requires understanding of the underlying physiology of the infant in transition. The situation is dynamic with changes occurring in systemic blood pressure, pulmonary pressures, myocardial function, and ductal shunt in the first postnatal days. New insights into the role of umbilical cord clamping in the transitional circulation have been provided by large clinical trials of early versus later cord clamping and a series of basic science reports describing the physiology in an animal model. Ultrasound assessment is invaluable in assessment of the physiology of the transition and can provide information about the size and shunt direction of the ductus arteriosus, the function of the myocardium and its filling as well as measurements of the cardiac output and an estimate of the state of peripheral vascular resistance. This information not only allows more specific treatment but it will often reduce the need for treatment.
Highlights
Martin Kluckow*Ultrasound assessment is invaluable in assessment of the physiology of the transition and can provide information about the size and shunt direction of the ductus arteriosus, the function of the myocardium and its filling as well as measurements of the cardiac output and an estimate of the state of peripheral vascular resistance
The cardiovascular system of the fetus is adapted to an in utero environment that is constant and stable with the low resistance placenta being a key part of the hemodynamic equilibrium
One definition is a mean blood pressure (MBP) less than 30 mm Hg in any gestation infant in the first postnatal days. This definition relates to previously observed pathophysiologic associations between cerebral injury and MBP less than 30 mm Hg at any time point in the first few postnatal days [3] and on more recent data aimed at maintenance of cerebral blood flow (CBF) measured by near-infrared spectroscopy [4, 5] the tenth centile for infants of all gestational ages by the third postnatal day is at or above 30 mm Hg, in more immature infants the 10th centile of MBP is lower than 30 mm Hg during the first 3 days [6]
Summary
Ultrasound assessment is invaluable in assessment of the physiology of the transition and can provide information about the size and shunt direction of the ductus arteriosus, the function of the myocardium and its filling as well as measurements of the cardiac output and an estimate of the state of peripheral vascular resistance. This information allows more specific treatment but it will often reduce the need for treatment
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